Issue 1771 in lilypond: Nested reverts fail for properties which aren't set as defaults in define-grobs.scm

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Defect Priority-Critical Regression

New issue 1771 by address@hidden: Nested reverts fail for properties  
which aren't set as defaults in define-grobs.scm
http://code.google.com/p/lilypond/issues/detail?id=1771

From the regtest property-nested-revert.ly:

\version "2.15.6"

\relative c' {
  f2 \glissando c
  \override Glissando #'bound-details #'right #'Y = #4
  f2 \glissando c |
  \override Glissando #'bound-details #'left #'Y = #-6
  f2 \glissando c
  \revert Glissando #'(bound-details right Y)
  f2 \glissando c
  \revert Glissando #'(bound-details left Y)
  f2 \glissando c
}

Neither \revert restores the default behaviour unless the initial overrides  
are defined in Glissando's bound-details defaults inside define-grobs.scm.

This is directly caused by the fix for issue 1063,  
http://git.savannah.gnu.org/gitweb/?p=lilypond.git;a=commit;h=4ea5963dd6b5289e57454bd2702b9527c06d6001,  
but slipped through since the regression test is flawed in using  
glissandos; they have no extent, so don't show up in regtest comparisons.

Attachments:
        lily-ec5de296.png  3.5 KB